When a machine asks "grub rescue>" how does one say yes?

I have a two Tera drive with two boot sectors. Both have 16.04's systems but I can't grub to fix them. I have GParted, but when I have it look, it says it can't do a data rescue? I have disks running and don't know what to change. Yesterday some one said type c. That did nothing, as did all the start command's I can think of. How do I use GRUB boot repair?

When it starts with GRUB RESCUE> How do I say yes? How do I start it? I never should have upped from 15. Yes I have a boot for 16.04 and it won't do anything but say unknown command. How do I start it?

Do you have a DVD with an Ubuntu installer on it, or a bootable USB stick with an Ubuntu installer?
I suggest that you insert it into your computer, reboot, and very early during the boot process press the function key (depending on your hardware) to select this one as boot medium.

When you see the choice "install Ubuntu" or "Try Ubuntu without installing" you should select "Try Ubuntu...".

Finally open a terminal window and issue the command
sudo fdisk -l
copy all output and paste it into this question document that we can see.

Thanks. The last time I entered command line it was in DOS. This AD FX -8320 x8 on 64 bit with 15.7 GiB will not see the USB stick. I've tryed all the choices. Now a new copy of the 16.04 ISO on a DVD might boot. I am shutting down to try that. Thanks for the help.

Well with a 16 .04 boot dvd and this two tera byte drive still cant get along. No boot. It got to the Ubunto count to five and sat there for twenty min's. So I put it on sdb/ cable and still no boot on the dvd. Should I trick it? It will boot to another drive with 16.04 on it. Should I do the DVD boot and then attach the two terabyte unit then re-scan the buss? Now I can't recall how to get grub rescue up? No dvd and only the bad drive I think. Nortons Disk Doctor would skip over the bad directory's and capture the files needed. Is there some thing like Samtics Disk Clinic?

When up and running on a 16.04 Hard disk GParted shows three partitions and all the info that shows where data is on the drive but it will not mount. I snapped a picture of the window. Can I attach it to an e-mail to you? I think it's screwing with the serial buss.

Grub cannot "fix" anything. Grub is the boot loader that does what the instructions in its setting tell to do, namely forwarding control to an operating system that is installed on a hard disk, eventually after showing a selection menu to ask which one of several operating systems to use.

Just to confirm that I understood correctly: If the 2 TB is connected to the system, then it does not boot at all. But if you plug it in later, then the details of the 2 TB disk are shown.

If I attach just the two tera it gets to that grub question and every thing I tried will not continue from there. THen when the CD is trying to boot it stops at the Ubuntu five count and runs there for a half hour so far. That is as long as I could stand to watch nothing happen. Do you want me to copy the info from gparted? What next?

Sorry, but I have problems understanding the status of your system based on your comments.

Please explain:

Is the 2 TB disk an internal or an external disk, if it is external, how is it connected?
What happens if you try booting without the 2 TB disk (i.e. boot from the 250 GB disk)?
What happens if you try booting from the 250 GB disk with the 2 TB disk connected?
What happens if you boot from a DVD without the 2 TB disk connected?
What happens if you boot from a DVD with the 2 TB disk connected?
How did you reach the "fdisk -l" output that shows both hard disks?

All the disks are internal. Throu a cable.
By it self it gets to the grub rescue> and stops. I cant get to go from there. (Boot the two fifty and the 2 Tera does not show up.)
It boots fine but the two Tera does not show up.
It stops booting and runs in a loop at the Ubuntu five count. Last time I let it run for half an hour.
Haven't tried that.
Like I said I connected everything and left the power off the two Terra until booted on the other drive. Then connected it and re-scan the bus.
Now the left hand icons have new ones. If I open a file, the left side has first, under the trash is a mostly black icon called system reserved and the eject button.
Then a icon for two computers and Network.
Then the next has four drive icon's. the 144GB, 532GB, 950GB, and Computer (no button) and the boot dvd for Ubuntu 16.04.2 L...